MEXICO CITY (AFP) - Russian opposition activist and chess legend Garry Kasparov urged the international community Wednesday to make President Vladimir Putin respect the sovereignty of nations after Moscow's takeover of Crimea.

Speaking at an event in Mexico City, Kasparov said the quick referendum that led to Russia's annexation of the Ukrainian peninsula was an "act of blatant aggression." If the sovereignty of nations is violated, he said, "the entire system of international cooperation might be in jeopardy." "The prime task of the international community is to make sure that Mr.

Putin will be forced to play chess, because in chess there are rules," Kasparov said as he promoted a foundation that will bring chess to Latin American schools.

"He's very good at raising stakes all the time. I believe he has a very weak hand but he's very good in bluffing," he said, calling for tougher US and European sanctions against Russia.

Kasparov warned that Putin could go after other places with sizeable Russian populations.

"He would feel comfortable to go anywhere where he believes Russian-speaking minorities are in danger. That's exactly what triggered World War II," he said.

Kasparov retired from competitive chess in 2005 after dominating the game for about two decades. He became the youngest world champion aged 22 in 1985 and is considered one of the greatest chess players of all time.